Global Change Can Make Coastal Eutrophication Control in China More Difficult

Fast socio-economic development in agriculture and urbanization resulted in increasing nutrient export by rivers, causing coastal eutrophication in China. In addition, climate change may affect hydrology, and as a result, nutrient flows from land to sea. This study aims at a better understanding of how future socio-economic and climatic changes may affect coastal eutrophication in China. We modeled river export of total dissolved nitrogen (TDN) and phosphorus (TDP) in 2050 for six scenarios combining socio-economic pathways (SSPs) and Representative Concentration Pathways (RCPs). We used the newly developed MARINA 2.0 (Model to Assess River Inputs of Nutrients to seAs) model. We found that global change can make coastal eutrophication control in China more difficult. In 2050 coastal waters may be considerably more polluted or considerably cleaner than today depending on the SSP-RCP scenarios. By 2050, river export of TDN and TDP is 52% and 56% higher than in 2012, respectively, in SSP3-RCP8.5 (assuming large challenges for sustainable socio-economic development, and severe climate change). In contrast, river export of nutrients could be 56% (TDN) and 85% (TDP) lower in 2050 than in 2012 in SSP1-RCP2.6 (assuming sustainable socio-economic development, and low climate change). Climate change alone may increase river export of nutrients considerably through hydrology: We calculate 24% higher river export of TDN and 16% higher TDP for the SSP2 scenario assuming severe climate change compared to the same scenario with low climate change (SSP2-RCP8.5 vs. SSP2-RCP2.6). Policies and relevant technologies combining improved nutrient management and climate mitigation may help to improve water quality in rivers and coastal waters of China.</p

Recent advancement in water quality indicators for eutrophication in global freshwater lakes

Eutrophication is a major global concern in lakes, caused by excessive nutrient loadings (nitrogen and phosphorus) from human activities and likely exacerbated by climate change. Present use of indicators to monitor and assess lake eutrophication is restricted to water quality constituents (e.g. total phosphorus, total nitrogen) and does not necessarily represent global environmental changes and the anthropogenic influences within the lake's drainage basin. Nutrients interact in multiple ways with climate, basin conditions (e.g. socio-economic development, point-source, diffuse source pollutants), and lake systems. It is therefore essential to account for complex feedback mechanisms and non-linear interactions that exist between nutrients and lake ecosystems in eutrophication assessments. However, the lack of a set of water quality indicators that represent a holistic understanding of lake eutrophication challenges such assessments, in addition to the limited water quality monitoring data available. In this review, we synthesize the main indicators of eutrophication for global freshwater lake basins that not only include the water quality constituents but also the sources, biogeochemical pathways and responses of nutrient emissions. We develop a new causal network (i.e. multiple links of indicators) using the DPSIR (drivers-pressure-state-impact-response) framework that highlights complex interrelationships among the indicators and provides a holistic perspective of eutrophication dynamics in freshwater lake basins. We further review the 30 key indicators of drivers and pressures using seven cross-cutting themes: (i) hydro-climatology, (ii) socio-economy, (iii) land use, (iv) lake characteristics, (v) crop farming and livestock, (vi) hydrology and water management, and (vii) fishing and aquaculture. This study indicates a need for more comprehensive indicators that represent the complex mechanisms of eutrophication in lake systems, to guide the global expansion of water quality monitoring networks, and support integrated assessments to manage eutrophication. Finally, the indicators proposed in this study can be used by managers and decision-makers to monitor water quality and set realistic targets for sustainable water quality management to achieve clean water for all, in line with Sustainable Development Goal 6

Current wastewater treatment targets are insufficient to protect surface water quality

The quality of global water resources is increasingly strained by socio-economic developments and climate change, threatening both human livelihoods and ecosystem health. With inadequately managed wastewater being a key driver of deterioration, Sustainable Development Goal (SDG) 6.3 was established to halve the proportion of untreated wastewater discharged to the environment by 2030. Yet, the impact of achieving SDG6.3 on global ambient water quality is unknown. Addressing this knowledge gap, we develop a high-resolution surface water quality model for salinity as indicated by total dissolved solids, organic pollution as indicated by biological oxygen demand and pathogen pollution as indicated by fecal coliform. Our model includes a novel spatially-explicit approach to incorporate wastewater treatment practices, a key determinant of in-stream pollution. We show that achieving SDG6.3 reduces water pollution, but is still insufficient to improve ambient water quality to below key concentration thresholds in several world regions. Particularly in the developing world, reductions in pollutant loadings are locally effective but transmission of pollution from upstream areas still leads to water quality issues downstream. Our results highlight the need to go beyond the SDG-target for wastewater treatment in order to achieve the overarching goal of clean water for all

Integrated Solutions for the Water-Energy-Land Nexus: Are Global Models Rising to the Challenge?

Increasing human demands for water, energy, food and materials, are expected to accentuate resource supply challenges over the coming decades. Experience suggests that long-term strategies for a single sector could yield both trade-offs and synergies for other sectors. Thus, long-term transition pathways for linked resource systems should be informed using nexus approaches. Global integrated assessment models can represent the synergies and trade-offs inherent in the exploitation of water, energy and land (WEL) resources, including the impacts of international trade and climate policies. In this study, we review the current state-of-the-science in global integrated assessment modeling with an emphasis on how models have incorporated integrated WEL solutions. A large-scale assessment of the relevant literature was performed using online databases and structured keyword search queries. The results point to the following main opportunities for future research and model development: (1) improving the temporal and spatial resolution of economic models for the energy and water sectors; (2) balancing energy and land requirements across sectors; (3) integrated representation of the role of distribution infrastructure in alleviating resource challenges; (4) modeling of solution impacts on downstream environmental quality; (5) improved representation of the implementation challenges stemming from regional financial and institutional capacity; (6) enabling dynamic multi-sectoral vulnerability and adaptation needs assessment; and (7) the development of fully-coupled assessment frameworks based on consistent, scalable, and regionally-transferable platforms. Improved database management and computational power are needed to address many of these modeling challenges at a global-scale

Panta Rhei benchmark dataset: socio-hydrological data of paired events of floods and droughts

As the adverse impacts of hydrological extremes increase in many regions of the world, a better understanding of the drivers of changes in risk and impacts is essential for effective flood and drought risk management and climate adaptation. However, there is currently a lack of comprehensive, empirical data about the processes, interactions and feedbacks in complex human-water systems leading to flood and drought impacts. Here we present a benchmark dataset containing socio-hydrological data of paired events, i.e., two floods or two droughts that occurred in the same area. The 45 paired events occurred in 42 different study areas and cover a wide range of socio-economic and hydro-climatic conditions. The dataset is unique in covering both floods and droughts, in the number of cases assessed, and in the quantity of socio-hydrological data. The benchmark dataset comprises: 1) detailed review style reports about the events and key processes between the two events of a pair; 2) the key data table containing variables that assess the indicators which characterise management shortcomings, hazard, exposure, vulnerability and impacts of all events; 3) a table of the indicators-of-change that indicate the differences between the first and second event of a pair. The advantages of the dataset are that it enables comparative analyses across all the paired events based on the indicators-of-change and allows for detailed context- and location-specific assessments based on the extensive data and reports of the individual study areas. The dataset can be used by the scientific community for exploratory data analyses e.g. focused on causal links between risk management, changes in hazard, exposure and vulnerability and flood or drought impacts. The data can also be used for the development, calibration and validation of socio-hydrological models. The dataset is available to the public through the GFZ Data Services (Kreibich et al. 2023, link for review: https://dataservices.gfz-potsdam.de/panmetaworks/review/923c14519deb04f83815ce108b48dd2581d57b90ce069bec9c948361028b8c85/).</p

Drought impacts on river salinity in the southern US : Implications for water scarcity

Hydrological droughts have a diverse range of effects on water resources. Whilst the impacts of drought on water quantity are well studied, the impacts on water quality have received far less attention. Similarly, quantifications of water scarcity have typically lacked water quality dimensions, whilst sectoral water uses are associated with both water quantity and quality requirements. Here we aim to combine these two elements, focussing on impacts of droughts on river salinity levels and including a salinity dimension in quantifications of water scarcity during drought and extreme drought conditions. The impact of historical droughts on river salinity (electrical conductivity (EC) was studied at 66 monitoring stations located across the Southern USA for 2000–2017. Salinity was found to increase strongly (median increase of 21%) and statistically significantly (p ≤ 0.05) during drought conditions for 59/66 stations compared to non-drought conditions. In a next step, a salinity dimension was added to water scarcity quantifications for 15 river basins in Texas. Water scarcity was quantified using data of sector water uses, water availability, river salinity levels and salinity thresholds for sector water uses. Results showed that the dominant factor driving water scarcity highly differed per basin. Increases in water scarcity were further compounded by drought-induced decreases in water availability, increases in sectoral water demands and increases in river water salinity. This study demonstrates that droughts are associated with important increases in river salinity, in addition to reduced water availability, and that both of these aspects should be considered when quantifying water scarcity. Alleviating water scarcity should therefore not only focus on increasing water availability and reducing water demands (quantity aspects), but also on improving water quality.</p

Impact of the 2018 drought on pharmaceutical concentrations and general water quality of the Rhine and Meuse rivers

Hydrological droughts are expected to increase in frequency and severity due to changing climate in several river basins. Recent severe droughts, like the 2018 drought in northwestern Europe, have shown major challenges for water management, not only in terms of water quantity, but also water quality. However, these water quality impacts have received far less attention, and limited understanding exists, in particular regarding concentration responses of emerging chemicals, such as pharmaceutical in surface waters under droughts. This study therefore shows the impacts of the 2018 drought on the water quality of the Rhine and Meuse rivers (Western Europe) focusing on a selection of water quality parameters relevant to multiple sectoral water uses and ecosystem health, i.e. water temperature, salinity and four pharmaceuticals (carbamazepine, metoprolol, ibuprofen and sulfamethoxazole). Surface water quality data of six monitoring stations (mainly in the Netherlands) were analyzed for the 2018 drought in comparison to the reference period 2014–2017. Our results show that low flow combined with high temperatures resulted in a general deterioration of surface water quality of both the Meuse and Rhine rivers during the 2018 drought. This was reflected by significant increases in water temperatures (average of +1.9 °C) and salinity levels (+11%). While we found higher concentrations of some pharmaceuticals (carbamazepine (+10%) and metoprolol (+29%)), these increases were statistically insignificant. The decline in water quality is primarily caused by limited dilution of the chemical load derived from point sources and salinity intrusion in the lower part of Rhine-Meuse delta. A comparison of the water quality responses of the Rhine and Meuse shows larger impacts for the rainfed Meuse river with lower summer flow, compared to the mixed rain- and snowmelt-fed Rhine river. Sustainable, transboundary river water management is essential to ensure water of suitable quality for different sectoral uses during future projected droughts

Impact of the 2018 drought on pharmaceutical concentrations and general water quality of the Rhine and Meuse rivers

Hydrological droughts are expected to increase in frequency and severity due to changing climate in several river basins. Recent severe droughts, like the 2018 drought in northwestern Europe, have shown major challenges for water management, not only in terms of water quantity, but also water quality. However, these water quality impacts have received far less attention, and limited understanding exists, in particular regarding concentration responses of emerging chemicals, such as pharmaceutical in surface waters under droughts. This study therefore shows the impacts of the 2018 drought on the water quality of the Rhine and Meuse rivers (Western Europe) focusing on a selection of water quality parameters relevant to multiple sectoral water uses and ecosystem health, i.e. water temperature, salinity and four pharmaceuticals (carbamazepine, metoprolol, ibuprofen and sulfamethoxazole). Surface water quality data of six monitoring stations (mainly in the Netherlands) were analyzed for the 2018 drought in comparison to the reference period 2014–2017. Our results show that low flow combined with high temperatures resulted in a general deterioration of surface water quality of both the Meuse and Rhine rivers during the 2018 drought. This was reflected by significant increases in water temperatures (average of +1.9 °C) and salinity levels (+11%). While we found higher concentrations of some pharmaceuticals (carbamazepine (+10%) and metoprolol (+29%)), these increases were statistically insignificant. The decline in water quality is primarily caused by limited dilution of the chemical load derived from point sources and salinity intrusion in the lower part of Rhine-Meuse delta. A comparison of the water quality responses of the Rhine and Meuse shows larger impacts for the rainfed Meuse river with lower summer flow, compared to the mixed rain- and snowmelt-fed Rhine river. Sustainable, transboundary river water management is essential to ensure water of suitable quality for different sectoral uses during future projected droughts

Impact of the 2018 drought on pharmaceutical concentrations and general water quality of the Rhine and Meuse rivers

Hydrological droughts are expected to increase in frequency and severity due to changing climate in several river basins. Recent severe droughts, like the 2018 drought in northwestern Europe, have shown major challenges for water management, not only in terms of water quantity, but also water quality. However, these water quality impacts have received far less attention, and limited understanding exists, in particular regarding concentration responses of emerging chemicals, such as pharmaceutical in surface waters under droughts. This study therefore shows the impacts of the 2018 drought on the water quality of the Rhine and Meuse rivers (Western Europe) focusing on a selection of water quality parameters relevant to multiple sectoral water uses and ecosystem health, i.e. water temperature, salinity and four pharmaceuticals (carbamazepine, metoprolol, ibuprofen and sulfamethoxazole). Surface water quality data of six monitoring stations (mainly in the Netherlands) were analyzed for the 2018 drought in comparison to the reference period 2014–2017. Our results show that low flow combined with high temperatures resulted in a general deterioration of surface water quality of both the Meuse and Rhine rivers during the 2018 drought. This was reflected by significant increases in water temperatures (average of +1.9 °C) and salinity levels (+11%). While we found higher concentrations of some pharmaceuticals (carbamazepine (+10%) and metoprolol (+29%)), these increases were statistically insignificant. The decline in water quality is primarily caused by limited dilution of the chemical load derived from point sources and salinity intrusion in the lower part of Rhine-Meuse delta. A comparison of the water quality responses of the Rhine and Meuse shows larger impacts for the rainfed Meuse river with lower summer flow, compared to the mixed rain- and snowmelt-fed Rhine river. Sustainable, transboundary river water management is essential to ensure water of suitable quality for different sectoral uses during future projected droughts

Impact of the 2018 drought on pharmaceutical concentrations and general water quality of the Rhine and Meuse rivers

Hydrological droughts are expected to increase in frequency and severity due to changing climate in several river basins. Recent severe droughts, like the 2018 drought in northwestern Europe, have shown major challenges for water management, not only in terms of water quantity, but also water quality. However, these water quality impacts have received far less attention, and limited understanding exists, in particular regarding concentration responses of emerging chemicals, such as pharmaceutical in surface waters under droughts. This study therefore shows the impacts of the 2018 drought on the water quality of the Rhine and Meuse rivers (Western Europe) focusing on a selection of water quality parameters relevant to multiple sectoral water uses and ecosystem health, i.e. water temperature, salinity and four pharmaceuticals (carbamazepine, metoprolol, ibuprofen and sulfamethoxazole). Surface water quality data of six monitoring stations (mainly in the Netherlands) were analyzed for the 2018 drought in comparison to the reference period 2014–2017. Our results show that low flow combined with high temperatures resulted in a general deterioration of surface water quality of both the Meuse and Rhine rivers during the 2018 drought. This was reflected by significant increases in water temperatures (average of +1.9 °C) and salinity levels (+11%). While we found higher concentrations of some pharmaceuticals (carbamazepine (+10%) and metoprolol (+29%)), these increases were statistically insignificant. The decline in water quality is primarily caused by limited dilution of the chemical load derived from point sources and salinity intrusion in the lower part of Rhine-Meuse delta. A comparison of the water quality responses of the Rhine and Meuse shows larger impacts for the rainfed Meuse river with lower summer flow, compared to the mixed rain- and snowmelt-fed Rhine river. Sustainable, transboundary river water management is essential to ensure water of suitable quality for different sectoral uses during future projected droughts